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https://github.com/packjpg/packJPG

A compression program for further compressing JPEG image files
https://github.com/packjpg/packJPG

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A compression program for further compressing JPEG image files

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README 

        
packJPG v2.5k (01/22/2016)

~~~~~~~~~~~~~~~~~~~~~~~~~~



packJPG is a compression program specially designed for further

compression of JPEG images without causing any further loss. Typically

it reduces the file size of a JPEG file by 20%.



LGPL v3 license and special permissions

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



All programs in this package are free software; you can redistribute 

them and/or modify them under the terms of the GNU Lesser General Public 

License as published by the Free Software Foundation; either version 3 

of the License, or (at your option) any later version. 



The package is distributed in the hope that it will be useful, but 

WITHOUT ANY WARRANTY; without even the implied warranty of 

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser 

General Public License for more details at 

http://www.gnu.org/copyleft/lgpl.html. 



If the LGPL v3 license is not compatible with your software project you 

might contact us and ask for a special permission to use the packJPG 

library under different conditions. In any case, usage of the packJPG 

algorithm under the LGPL v3 or above is highly advised and special 

permissions will only be given where necessary on a case by case basis. 

This offer is aimed mainly at closed source freeware developers seeking 

to add PJG support to their software projects. 



Copyright 2006...2014 by HTW Aalen University and Matthias Stirner.



Usage of packJPG

~~~~~~~~~~~~~~~~



JPEG files are compressed and PJG files are decompressed using this

command:



 "packJPG [file(s)]"



packJPG recognizes file types on its own and decides whether to compress

(JPG) or decompress (PJG). For unrecognized file types no action is

taken. Files are recognized by content, not by extension.



packJPG supports wildcards like "*.*" and drag and drop of multiple 

files. Filenames for output files are created automatically. In default

mode, files are never overwritten. If a filename is already in use,

packJPG creates a new filename by adding underscores.



If "-" is used as a filename input from stdin is assumed and output is

written to stdout. This can be useful for example if jpegtran is to be

used as a preprocessor.



Usage examples:



 "packJPG *.pjg"

 "packJPG lena.jpg"

 "packJPG kodim??.jpg"

 "packJPG - < sail.pjg > sail.jpg"



Command line switches

~~~~~~~~~~~~~~~~~~~~~



 -ver  verify files after processing

 -v?   level of verbosity; 0,1 or 2 is allowed (default 0)

 -np   no pause after processing files

 -o    overwrite existing files

 -p    proceed on warnings

 -d    discard meta-info



By default, compression is cancelled on warnings. If warnings are 

skipped by using "-p", most files with warnings can also be compressed, 

but JPEG files reconstructed from PJG files might not be bitwise 

identical with the original JPEG files. There won't be any loss to 

image data or quality however.



Unnecessary meta information can be discarded using "-d". This reduces 

compressed files' sizes. Be warned though, reconstructed files won't be 

bitwise identical with the original files and meta information will be 

lost forever. As with "-p" there won't be any loss to image data or 

quality. 



There is no known case in which a file compressed by packJPG (without 

the "-p" option, see above) couldn't be reconstructed to exactly the 

state it was before. If you want an additional layer of safety you can 

also use the verify option "-ver". In this mode, files are compressed, 

then decompressed and the decompressed file compared to the original 

file. If this test doesn't pass there will be an error message and the 

compressed file won't be written to the drive. 



Please note that the "-ver" option should never be used in conjunction 

with the "-d" and/or "-p" options. As stated above, the "-p" and "-d" 

options will most likely lead to reconstructed JPG files not being 

bitwise identical to the original JPG files. In turn, the verification 

process may fail on various files although nothing actually went wrong. 



Usage examples:



 "packJPG -v1 -o baboon.pjg"

 "packJPG -ver lena.jpg"

 "packJPG -d tiffany.jpg"

 "packJPG -p *.jpg"



Known Limitations 

~~~~~~~~~~~~~~~~~ 



packJPG is a compression program specially for JPEG files, so it doesn't 

compress other file types.



packJPG has low error tolerance. JPEG files might not work with packJPG 

even if they work perfectly with other image processing software. The 

command line switch "-p" can be used to increase error tolerance and 

compatibility.



If you try to drag and drop to many files at once, there might be a 

windowed error message about missing privileges. In that case you can 

try it again with less files or consider using the command prompt. 

packJPG has been tested to work perfectly with thousands of files from 

the command line. This issue also happens with drag and drop in other 

applications, so it might not be a limitation of packJPG but a 

limitation of Windows.



Compressed PJG files are not compatible between different packJPG 

versions. You will get an error message if you try to decompress PJG 

files with a different version than the one used for compression. You 

may download older versions of packJPG from:

http://www.elektronik.htw-aalen.de/packJPG/binaries/old/



Open source release / developer info

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



The packJPG source codes is found inside the "source" subdirectory. 

Additional documents aimed to developers, containing detailed 

instructions on compiling the source code and using special 

functionality, are included in the "packJPG" subdirectory. 

 



History

~~~~~~~



v1.9a (04/20/2007) (non public)

 - first released version

 - only for testing purposes



v2.0  (05/28/2007) (public)

 - first public version of packJPG

 - minor improvements to overall compression

 - minor bugfixes



v2.2  (08/05/2007) (public)

 - around 40% faster compression & decompression

 - major improvements to overall compression (around 2% on average)

 - reading from stdin, writing to stdout

 - smaller executable

 - minor bugfixes

 - various minor improvements

 

v2.3  (09/18/2007) (public)

 - compatibility with JPEG progressive mode

 - compatibility with JPEG extended sequential mode

 - compatibility with the CMYK color space

 - compatibility with older CPUs

 - around 15% faster compression & decompression 

 - new switch: [-d] (discard meta-info)

 - various bugfixes



v2.3a (11/21/2007) (public)

 - crash issue with certain images fixed

 - compatibility with packJPG v2.3 maintained



v2.3b (12/20/2007) (public)

 - some minor errors in the packJPG library fixed

 - compatibility with packJPG v2.3 maintained

 

v2.4 (03/24/2010) (public)

 - major improvements (1%...2%) to overall compression

 - around 10% faster compression & decompression

 - major improvements to JPG compatibility

 - size of executable reduced to ~33%

 - new switch: [-ver] (verify file after processing)

 - new switch: [-np] (no pause after processing)

 - new progress bar output mode

 - arithmetic coding routines rewritten from scratch

 - various smaller improvements to numerous to list here

 - new SFX (self extracting) archive format

 

v2.5 (11/11/2011) (public)

 - improvements (~0.5%) to overall compression

 - several minor bugfixes

 - major code cleanup

 - removed packJPX from the package

 - added packARC to the package

 - packJPG is now open source!

 

v2.5a (11/21/11) (public)

 - source code compatibility improvements (Gerhard Seelmann)

 - avoid some compiler warnings (Gerhard Seelmann)

 - source code clean up (Gerhard Seelmann)

 

v2.5b (01/27/12) (public)

 - further removal of redundant code

 - some fixes for the packJPG static library

 - compiler fix for Mac OS (thanks to Sergio Lopez)

 - improved compression ratio calculation

 - eliminated the need for temp files

 

v2.5c (04/13/12) (public)

 - various source code optimizations

 

v2.5d (07/03/12) (public)

 - fixed a rare bug with progressive JPEG

 

v2.5e (07/03/12) (public)

 - some minor source code optimizations

 - changed packJPG licensing to LGPL

 - moved packARC to a separate package

 

v2.5f (02/24/13) (public)

 - fixed a minor bug in the JPG parser (thanks to Stephan Busch)

 

v2.5g (09/14/13) (public)

 - fixed a rare crash bug with manipulated JPEG files

 

v2.5h (12/07/13) (public)

 - added a warning for inefficient huffman coding (thanks to Moinak Ghosh)

 

v2.5i (12/26/13) (public)

 - fixed possible crash with malformed JPEG (thanks to Moinak Ghosh)

 

v2.5j (01/15/14) (public)

 - various source code optimizations (using cppcheck)



v2.5k (01/22/16) (public)

 - Updated contact info

 - fixed a minor bug



Acknowledgements

~~~~~~~~~~~~~~~~



packJPG is the result of countless hours of research and development. It

is part of my final year project for Hochschule Aalen.



Prof. Dr. Gerhard Seelmann from Hochschule Aalen supported my

development of packJPG with his extensive knowledge in the field of data

compression. Without his advice, packJPG would not be possible.



The official developer blog for packJPG is hosted by encode.ru.



packJPG logo and icon are designed by Michael Kaufmann.



Contact

~~~~~~~



The official developer blog for packJPG:

 http://packjpg.encode.ru/

 

For questions and bug reports:

 packjpg (at) matthiasstirner.com



____________________________________

packJPG by Matthias Stirner, 01/2016